X-ray diffraction methods will be used to elucidate the molecular structures of chemically-different drugs used in treatment of grand and petit mal epilepsies, in order to establish the stereochemical determinants of biological activity. Attempts will also be made to determine the three-dimensional structures of enkephalins, and to discover possible stereochemical similarities with morphine-type analgesics. The hypothalamic hormone somatostatin will also be studied. In addition, we shall elucidate the molecular conformation of the dopaminergic compound bromocriptine, and stereochemical comparisons with dopamine and other dopaminergics will be made. Our previous work has conclusively demonstrated that a number of chemically-different, clinically-useful anticonvulsants have striking stereochemical similarities in their three-dimensional conformational structures. These agents include diphenylhydantoin, diazepam, procyclidine, diphenylsilanediol, the ring-opened phenacemide compounds, and a new 2,4-benzodiazepine. It thus appears that the efficacies of these diverse molecules against grand mal epilepsy are primarily due to the stereochemical components they have in common. We shall now study additional active agents, representing four more chemically-different families of compounds and compare their structures in detail with the above anticonvulsants in order to further refine correlations between biological activity and molecular stereochemistry. In addition, we shall use the knowledge gained to initiate the syntheses of new anticonvulsant drugs, hopefully with more potency and less toxicity than the presently available agents. Molecular structure studies will also be performed on agents used in the treatment of petit mal epilepsy. The drugs trimethadione and ethosuximide, two chemically-different but equally potent anti-petit mal drugs, will be structurally elucidated and their stereochemical features compared. Methsuximide and phensuximide will also be considered.